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We consider the model, proposed by Dawidowicz and Zalasiński, describing the interactions between the heterotrophic and autotrophic organisms coexisting in a terrestrial environment with available oxygen. We modify this model by assuming intraspecific competition between heterotrophic organisms. Moreover, we introduce a diffusion of both types of organisms and oxygen. The basic properties of the extended model are examined and illustrated by numerical simulations.
Fractional derivative or fractional calculus plays a significant role in theoretical modeling of scientific and engineering problems. However, only relatively low order fractional derivatives are used at present. In general, it is not obvious what role a high fractional derivative can play and how to make use of arbitrarily high-order fractional derivatives. This work introduces arbitrarily high-order fractional partial differential equations (PDEs) to describe fractional hyperdiffusions. The fractional...
HIV infection is multi-faceted and a multi-step process. The virus-induced pathogenic
mechanisms are manifold and mediated through a range of positive and negative feedback
regulations of immune and physiological processes engaged in virus-host interactions. The
fundamental questions towards understanding the pathogenesis of HIV infection are now
shifting to ‘dynamic’ categories: (i) why is the HIV-immune response equilibrium finally
disrupted? (ii)...
Neutropenia is a significant dose-limiting toxicity of cancer
chemotherapy, especially in dose-intensified regimens. It is
widely treated by injections of Granulocyte Colony-Stimulating
Factor (G-CSF). However, optimal schedules of G-CSF administration
are still not determined. In order to aid in identifying more
efficacious and less neutropenic treatment protocols, we studied a
detailed physiologically-based computer model of granulopoiesis,
as affected by different treatment schedules of doxorubicin...
We consider the inverse problem of determining how the physiological structure of a harvested population evolves in time, and of finding the time-dependent effort to be expended in harvesting, so that the weighted integral of the density, which may be, for example, the total number of individuals or the total biomass, has prescribed dynamics. We give conditions for the existence of a unique, global, weak solution to the problem. Our investigation is carried out using the method of characteristics...
Gliomas are highly invasive brain tumors that exhibit high and spatially heterogeneous
cell proliferation and motility rates. The interplay of proliferation and migration
dynamics plays an important role in the invasion of these malignant tumors. We analyze the
regulation of proliferation and migration processes with a lattice-gas cellular automaton
(LGCA). We study and characterize the influence of the migration/proliferation dichotomy
(also known...
In this contribution we add a unilateral term to the Thomas model and investigate the resulting Turing patterns. We show that the unilateral term yields nonsymmetric and irregular patterns. This contrasts with the approximately symmetric and regular patterns of the classical Thomas model. In addition, the unilateral term yields Turing patterns even for smaller ratio of diffusion constants. These conclusions accord with the recent findings about the influence of the unilateral term in a model for...
Relaxation oscillations are limit cycles with two clearly different
time scales. In this article the spatio-temporal dynamics of a
standard prey-predator system in the parameter region of relaxation
oscillation is investigated. Both prey and predator population are
distributed irregularly at a relatively high average level between a
maximal and a minimal value. However, the slowly developing complex
pattern exhibits a feature of “inverse excitability”: Both
populations show collapses which occur...
In this paper, we study the numerical approximation of a size-structured population model
whose dependency on the environment is managed by the evolution of a vital resource. We
show that this is a difficult task: some numerical methods are not suitable for a
long-time integration. We analyze the reasons for the failure.
We introduce a phenomenological model for anti-angiogenic therapy in the treatment of metastatic cancers. It is a structured transport equation with a nonlocal boundary condition describing the evolution of the density of metastases that we analyze first at the continuous level. We present the numerical analysis of a lagrangian scheme based on the characteristics whose convergence establishes existence of solutions. Then we prove an error estimate and use the model to perform interesting simulations...
We introduce a phenomenological model for anti-angiogenic therapy in the treatment of metastatic cancers. It is a structured transport equation with a nonlocal boundary condition describing the evolution of the density of metastases that we analyze first at the continuous level. We present the numerical analysis of a lagrangian scheme based on the characteristics whose convergence establishes existence of solutions. Then we prove an error estimate and use the model to perform interesting simulations...
We introduce a phenomenological model for anti-angiogenic therapy in the treatment of metastatic cancers. It is a structured transport equation with a nonlocal boundary condition describing the evolution of the density of metastases that we analyze first at the continuous level. We present the numerical analysis of a lagrangian scheme based on the characteristics whose convergence establishes existence of solutions. Then we prove an error estimate and use the model to perform interesting simulations...
This article is devoted to the construction of a mathematical model describing the early
formation of atherosclerotic lesions. The early stage of atherosclerosis is an
inflammatory process that starts with the penetration of low density lipoproteins in the
intima and with their oxidation. This phenomenon is closely linked to the local blood flow
dynamics. Extending a previous work [5] that was mainly restricted to a
one-dimensional setting, we couple...
We study a class of parabolic-ODE systems modeling tumor growth, its mathematical modeling and the global in time existence of the solution obtained by the method of Lyapunov functions.
The paper is devoted to mathematical modelling and numerical computations of a
nonstationary
free boundary problem. The model is based on processes of molecular diffusion of
some
products of chemical decomposition of a solid organic substance concentrated in
bottom sediments.
It takes into account non-stationary multi-component and multi-stage chemical
decomposition of
organic substances and the processes of sorption desorption under aerobic and
anaerobic conditions.
Such a model allows one to...
In this article, we propose an integrated model for oxygen transfer into the blood, coupled with a lumped mechanical model for the ventilation process. Objectives. We aim at investigating oxygen transfer into the blood at rest or exercise. The first task consists in describing nonlinear effects of the oxygen transfer under normal conditions. We also include the possible diffusion limitation in oxygen transfer observed in extreme regimes involving parameters such as alveolar and venous blood oxygen...
In this paper we are interested in a mathematical model of migration of grass eels in an estuary. We first revisit a previous model proposed by O. Arino and based on a degenerate convection-diffusion equation of parabolic-hyperbolic type with time-varying subdomains. Then, we propose an adapted mathematical framework for this model, we prove a result of existence of a weak solution and we propose some numerical simulations.
Plant growth occurs due to cell proliferation in the meristem. We model the case of
apical meristem specific for branch growth and the case of basal meristem specific for
bulbous plants and grass. In the case of apical growth, our model allows us to describe
the variety of plant forms and lifetimes, endogenous rhythms and apical domination. In the
case of basal growth, the spatial structure, which corresponds to the appearance of
leaves, results...
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